TEF6901A_3 © NXP B.V. 2008. All rights reserved.
Product data sheet Rev. 03 — 20 March 2008 41 of 107
NXP Semiconductors
TEF6901A
Integrated car radio
The fully integrated IF2 filter of the TEF6901A has to be aligned in order to achieve the
optimum performance at all ambient conditions.
8.2.10.1 Factory alignment of bits IFCAP[3:0]
FM IF filter operation point alignment: data byte IFCAP: a single alignment of the FM IF
filter operation range secures an accurate and continuous frequency setting over the full
temperature range and all FM bands.
1. Set bit IFCAPA to logic 1 to disable internal IFCAP control
2. Decrease IFCAP from 15 downwards until I
2
C-bus read bit IFCAPG (read byte 5; ID)
changes from logic 1 to logic 0
3. Save this IFCAP setting as alignment value
4. Set bit IFCAPA to logic 0 to return to normal operation
8.2.10.2 Initialization of the radio
During radio initialization bit IFCAPA (is logic 1) is used for writing the stored IFCAP[3:0]
value. Afterwards set bit IFCAPA to a logic 0 to start normal operation. Writing of the
IFCAP byte with the alignment value is allowed during radio operation but requires a
setting of bit IFCAPA to logic 0.
8.2.10.3 Factory alignment of IFCF
FM IF filter center frequency alignment: data byte IFCF: to correct IF frequency errors
caused by an error in the crystal frequency the alignment is preferably performed for every
FM band in use. A test frequency in the center of the band is preferred. An accurate
alignment result is realized by testing for symmetrical filter attenuation.
1. Set RF generator level V
RF
= 200 µV
2. Set bit IFCFA to logic 1 to enable fast settling of the filter frequency
3. Set bit IFNBW to logic 1 for accuracy (filter is set to narrow 57 kHz bandwidth)
4. Test high side of filter curve: tune to f
RF
− 50 kHz (Europe/USA) or f
RF
+ 33.3 kHz
(Japan/OIRT)
5. Change IFCF from 0 to 63 and note the level read result (level voltages)
6. Test low side of filter curve: tune to f
RF
+ 50 kHz (Europe/USA) or f
RF
− 33.3 kHz
(Japan/OIRT)
7. Change IFCF from 0 to 63 and note the level voltages
8. Find the IFCF value where both level curves cross (lowest difference) and save this
IFCF value
Table 47. IFCAP - data byte 08h bit description
Bit Symbol Description
7 IFCAPA FM IF filter capacitor align
0 = standard operation
1 = align mode and initialization mode (auto correct disabled)
6 to 4 - reserved; 0 = normal operation
3 to 0 IFCAP[3:0] IF filter capacitor. Setting of FM IF filter capacitor value by means of
bit IFCAPG of read data byte 5, ID; see
Table 19 (For initialization set
IFCAPA = 1. For alignment set IFCAPA = 1 and check, when read bit
IFCAPG changes from logic 0 to logic 1).
